It's because Japan doesn't actually use Scart, but something that looks exactly like Scart but a couple of pins are reversed. It's commonly called "J21".
In the box for the Framemeister is a converter that connects J21 and converts it to the mini-DIN input on the Framemeister. All you need to do is get a different version of that converter that connects PAL Scart to mini-DIN.
Something like this.
Your PAL scart cables will be fine. In fact, as a North American, we had neither Scart nor J21, but because PAL Scart cables are so much easier to find cables and switchers for, that is what I invested in (even though we're NTSC!.. the TV format is irrelevant when considering these connectors)
XRGB mini is definitely only for people with HD sets. No need for any special device if you have a CRT tube TV with RGB input (Scart or otherwise).
But I'll say that flexibility is damn nice. I have a PVM tube TV which I love, and I also have a XRGB mini connected to my HDTV plasma. And actually... the HDTV is my daily driver. I value the big screen, geometrically perfect image. But others may value different qualities there.
All your SCART cables are fine if you have the cable I linked above.... but your NES will need to be modded for RGB. You can input composite to the XRGB mini if you have nothing else... it's not bad but not good.
If you are in Europe you will need to get a power converter (incidentally, we don't in North America... the voltage between Japan and North America is so close that AV adapters compensate).
But the picture cables are all the same. No need to get NTSC consoles unless you want NTSC versions of games with the right timing. The PAL consoles can connect to the XRGB mini or a CRT tube TV all the same.
